Reliability assessment of dependent competing risks with mixed shock model

This paper studies reliability models for systems subject to dependent competing risks under the impact from a mixed shock model. Two dependent failure processes are soft failure due to degradation process, and hard failure due to random shocks. The shocks contain fatal shocks that cause the system failure immediately, and nonfatal shocks that impact on the system in three different ways simultaneously: 1) damage the unit by increasing the degradation instantaneously, 2) speed up the deterioration by accelerating the degradation rate, and 3) weaken the unit by reducing the hard failure threshold. While the first impact of nonfatal shocks comes from each individual shocks, the other two impacts are realized when the condition for a mixed shock model is satisfied. The mixed shock model includes two shock models: extreme shock model, and m-shock model. According to the proposed model, the degradation rate and the hard failure threshold shift simultaneously when at least one of these two shock models occurs. An example using MEMS devices illustrates the effectiveness of the proposed model with sensitivity analysis.